1. Field of the Invention
The invention is directed to a hyperspectral or multispectral imaging systems and apparatus for performing real-time and/or near real-time assessment and monitoring of one or more physiologic parameters. The invention is also directed to method of analyzing the hyperspectral and multispectral data to provide specific diagnoses and treatment options in, for example, shock and impending shock, hypovolemia, hemodynamic compromise, physiological derangement, dehydration, and hypothermia.
2. Description of the Background
Early detection of metabolic shock regardless of etiology is critical for a variety of civilian and military medical environments. Acute hemorrhage and subsequent circulatory collapse (shock) account for about 50% of the deaths on the battlefield and the forward operating table, a statistic that has remained relatively unchanged since World War I. In addition, hemorrhage is the primary cause of death in about 30% of injured soldiers who die from wounds. Likewise, uncontrolled hemorrhage accounts for up to 82% of the early operative deaths from trauma in the civilian arena. However, the mortality rate in combat casualties drops to 2% to 4% if the trauma patient is stabilized through surgery. It is therefore clear that the ability to provide an early diagnosis of shock significantly reduces mortality and morbidity associated with shock in both civilian and military settings.
Hemorrhagic shock is typically identified by the degree of hypotension, nonspecific signs and subjective symptoms such as cold clammy skin, pallor, weak thready pulse, unstable vital signs, and diminished mentation that develop as a result of blood loss. Similar symptoms are seen for other types of shock. The impact of shock is a mismatch between supply and demand leading to alterations in cellular metabolism in various tissues. All of these result from the insufficiency of the circulation to meet metabolic demands.
It is clear that past a certain point, shock becomes irreversible. For military applications, particularly in the battlefield, it is extremely useful to have indications as to which injured soldiers were expectant and which ought to be given therapy. Significant effort has been placed toward the delineation of criteria for predicting impending hemodynamic decompensation and for determining the irreversibility of shock in a variety of human and animal models. Similarly, information that could be used to assess other injury, exposure to chemical or biological agents, exhaustion, dehydration, nutritional state, level of mental or emotional stress, pharmacological agents, exposure to toxic agents such as carbon monoxide would be useful in both battlefield and civilian settings.
Adequate triage and diagnosis are key to appropriate application of potentially life saving therapeutic countermeasures. In the face of a chemical or biological exposure, it will be both critical and difficult to rapidly and accurately assess the hemodynamic status of wounded or affected individuals. Cumbersome chemical biowarfare (CBW) personal protective gear may prevent medical personnel or first responders from the access required for standard assessment of casualties who may also be wearing CBW gear. Taking a pulse or measuring blood pressure may be impossible. Any device placed in contact with a potentially contaminated individual may also be contaminated and may not be able to be reused without onerous cleansing measures or disposable covers. Therefore, the development and deployment of a remote sensing technology to provide physiologic and hemodynamic assessment in such circumstances would be highly advantageous. For maximum utility, such a technology would provide a hand-held, robust, turnkey system that could provide near-real time information. It would require minimal operator dexterity and would be operable by an end-user in CBW attire.
Profound acidosis, base deficit or rates of change of base deficit have all been associated with non-survivability, but it is well known that these occur late in the progression of shock. In addition, to date, the assessment of these parameters has required blood sample and laboratory equipment, which restricts the use of such tests for first responders. Other parameters such as profound hypotension or the onset of severe bradycardia or other significant dysrhythmias are often seen in shock immediately prior to a terminal event but cannot reliably provide sufficient advance notice to permit successful intervention. Milder degrees of hypotension or rhythm disturbances can be associated with either survival or death and offer no prognostic information. Thus, there is an outstanding need for monitoring devices that would provide earlier information about likely outcomes for a patient's response to shock.
Since the appearance of hypotension and reduced oxygen delivery reflect late events in the process of hemorrhagic shock, it is critical to identify physiological signals that are altered during the earliest time period of blood volume loss to provide an accurate assessment of the severity of shock. A common denominator in development of shock is inadequate oxygen delivery (DO2) to the tissue associated with reductions in blood flow (cardiac output) or metabolic alterations (reduced pH or base excess). Increased cardiac output and DO2 correlate well with survival while failure to stabilize cardiac output and DO2 is highly correlated with death. Therefore, approaches that include some indicator of oxygen delivery (e.g., stroke volume, cardiac output) represent better tools for the early prediction of circulatory shock than measurements currently used for this purpose.